RosettaCodeData/Task/Pattern-matching/Tcl/pattern-matching-2.tcl

31 lines
1.1 KiB
Tcl

datatype define Color = R | B
datatype define Tree = E | T color left val right
# balance :: Color -> Tree a -> a -> Tree a -> Tree a
proc balance {color left val right} {
datatype match $color $left $val $right {
case B [T R [T R a x b] y c] z d -> { T R [T B $a $x $b] $y [T B $c $z $d] }
case B [T R a x [T R b y c]] z d -> { T R [T B $a $x $b] $y [T B $c $z $d] }
case B a x [T R [T R b y c] z d] -> { T R [T B $a $x $b] $y [T B $c $z $d] }
case B a x [T R b y [T R c z d]] -> { T R [T B $a $x $b] $y [T B $c $z $d] }
case col a x b -> { T $col $a $x $b }
}
}
# insert :: Ord a => a -> Tree a -> Tree a
proc insert {x s} {
datatype match [ins $x $s] {
case [T _ a y b] -> { T B $a $y $b }
}
}
# ins :: Ord a => a -> Tree a -> Tree a
proc ins {x s} {
datatype match $s {
case E -> { T R E $x E }
case [T col a y b] -> {
if {$x < $y} { return [balance $col [ins $x $a] $y $b] }
if {$x > $y} { return [balance $col $a $y [ins $x $b]] }
return $s
}
}
}